Production of basic aluminum sulphate



ll atented titan "T, I Width train I tllElEtilTEldti. TEAGLEY, OlliPHILADELPHIA, PENNSYLVANIA,

ASSIGNOR, IIBY MESNE t thifiJEG'NMJENTS, TO THE GRASSELLI GHEIMICAIiCOMPANY, OF CLEVELAND, OHIO, .Ha.

conronarron or ionnawaian JPRUID'UCTTON 01F BASIC AL'UllHN'Ull/lSULPHATE This invention relates to basic alminum sulphate and itsproduction and has particu- 5 to say,

obgect of the invention to ce lar reference to a procedure wherebyaluminum sulphate of high basicity and purity may be readilymanufactured, and to the product of such procedure. llt is the majorprovide such a proure and product.

It is the desire in producing aluminum sulphate destined for certainuses, notably that or water purification, to make a material that ishighly basic, that is, contains a proportion of alumina, itl Cu greaterthan that required to give a neutral product. That is consideringaluminum sulphate, Al (S@,) as iil U iisO it is desirable that the ratioAl U :SO be materially greater than 1: 3.

T have tound'that it alumina hydrate in excess and substantially withoutacid insolubles be treated with sulphuric acid, even without pressuresabove atmospheric, and the solution concentrated, then, even though thematerials, particularly the alumina hydrate,

contain substantially no insolubles, e. g., hydrated silica, clay,silca, titanium oxide. etc., aluminum sulphate of high basicity is produced (the same being substantially tree from insolubles). Furthermore,I have found that the procedure may be successfully carried out whetheror not iron be present; and thus by the present method ll am enabled toproduce, depending upon whether or not the raw materials contain iron, aproduct commercially iron-tree or practically wholly iron-tree, and

substantialy free from insolubles in either case. In particular, it havefound that alumina hydrate will very readily go into solution, in asolution of the type suggested above, e. g, one produced by treatingalumina hydrate with sulphuric acid, to produce a highly basic alum,when the solution has atotal A1 0 content between 13% and 14.5%. Theformer is indicated by the solution having a density of 47 186. atboiling temperature, and the latter by the solution having a density of52 B. boiling temperature.

Without restricting the invention thereto, the following will serve asan example of practice in accordance therewith Application filed June995,

. To a quantity of sulphuric acid, strength desirably about 85%,contained in an acid proof tank equipped with steam coils is addedalumina hydrate practically free from acid insolubles, in an amount toprovide AhQ about to in excess of the theoretical amount necessary tocombine with the sulphuric acid to form normal aluminum. sulphate. Thehydrate may desirably be that known commercially as drate and containingapproximately 64% Al U The hydrate is added gradually, say in about ahalf hour, with continuous boiling. The reaction will cause the densityof the solution to increase from about cs. to 47 Be. at boilingtemperature. This rather dilute solution is now concentrated, byboiling, to 52 B. at boiling temperature. ple is now taken and thebasicity found by the well-known analytical methods. sicity should bebetween 15.0% and 17.3% after all the alumina has gone into solution.(Tn referring to basicity, as, say ll%, T mean that of the total AM),present, 1t'% is in excess of the amount necessary to give normal ingbeen attained, the boiling and concentrating are continued until thecontents of the reaction tanlrtest625 Be. at boiling temperature,indicating a total Al content of about lh%. 'llhe reaching of this pointindicates that the'aluminum sulphate has become suitably basic. The hotand fluid contents of the tank maynow be poured upon a suitable coolingtloor, cooled and solidified, and afterward ground in the regularmanner.

- Thus produced in accordance with the invention, the finished producthas a total alumina content of 18to 18.5 per cent, of which 2.7 to 3.2%are in excess of that required fornormal aluminum sulphate, so that theprodheavy alumina hy- The ba-- approximately 47 Ba, i

llltl 1s not only applicable to uot has a basicity of 15.0% to 17.3%,and has an insoluble content of less than 1%.

As before indicated, the above procedure materials containing no ironbut is also applicable to materials containing iron, it being the fact,I have found, that normal aluminum sulphate solution containing someiron will dissolve alumina hydrate. Thus, with the above procedure, whensulphuric acid and alumina hydrate both practicallyfree from iron areused (e. g., the acid may contain 001% Fe or less and similarlywith thehydrate), a product practically free from iron can be produced; whilewith the materials containing some iron a commercially iron-free highlybasic alum can be produced. By way of illustration, merely, apractically iron-free product may contain 004% iron, and a commerciallyironfree product contain .4 to .7 iron, the iron being expressed as Fe OI claim:

1. The method of producing basic alumi num sulphate substantially freefrom insolubles which comprises adding to sulphuric acidheavy aluminahydrate, substantially free from insolubles, in excess of that requiredto react with the acid to produce normal aluminum sulphate,and-concentrating the solution.

content of about 13%, and boiling the solution to concentrate the sameto a density of about 625 B., at boiling temperature.

6. As an article of manufacture, basic aluminum sulphate substantiallyfree from ins'olubles and having a percentage basicity of 15.0% to17.3%.

7. As an article of manufacture, basic aluminum sulphate substantiallyfree from insolubles and iron and having a percentage basicity of 15.0%to 17.3%.

In testimon whereof I afiix my signature.

HESTER C. FEAG LEY.

2. The method of producing iron-free basic aluminum sulphatesubstantially free from insolubles which comprises adding to ironfreesulphuric acid, heavy alumina hydrate, substantially free from iron andinsolubles, in excess of that required to react with the acid to producenormal aluminum sulphate, and concentrating the solution.

3. The method of producing basic aluminum sulphate which comprisespreparing an aluminum sulphate solution having a basicity of 15.0% to 1.3% and a total alumina content of approximately 13%, by adding tosulphuric acid heavy alumina tiall free from insolubles, in excessofthat reqinred to react with the acid to produce norma aluminumsulphate, and concentrating the solution.

. ba sicity of 15.0% to 17.3%

i num sulphate which comprises adding 4. The method of producing ironfree basic' aluminum sulphate which comprises preparin an aluminumsulphate solution having a and a total alu-' mina content ofapproximately 13%, by adding to iron free sulphuric acid heavy aluminahydrate, substantially free from iron and insolubles, in excess of thatrequired to react with the acid to produce normal aluminum sulphate, andboiling the solution to concen trate the same until the alumina contentis about 18%.

5. The method of producing basic alumiabout 35% sulphuric acid, aluminahydrate to we the solution a basicity on a 30 136. basis of 15.0% to17.3% and a total alumina hydrate, substan- I

